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Ireland's political and cultural magazine
66 October/November 2023 October/November 2023 PB
The carvings suggest that their creators
— more than six thousand years ago —
understood the precession of the equinoxes,
whose discovery has been credited to
Hipparchus 4000 years later
I
t was astronomy that cracked the mystery
in the end. After four years of research
into three decorated stones outside
Westport, it seemed that they could be a
map of the stars. Searching the current
night skies for a match was not producing any
results until I realised that the night skies had
of course changed over thousands of years.
Setting the date at 4,200 BC for the location of
Boheh just outside Westport, the astronomy
software immediately produced a stunning
result: the Southern Cross was standing right
on the southern horizon.
Wait, most people say. The Southern Cross
is only visible from below the equator. That’s
true now, but it was not true 6,200 years ago.
For around that time, the Southern Cross was
clearly visible, if slowly disappearing, over the
southern horizon as seen from Ireland. Three
Stones: The Cross and the Circle is the story of
the re-discovery of the meaning of these three
carved stones.
The Lankill stone, the Cross Man stone and
the Boheh stand within a few kilometres of
each other in the hills and foothills around
Knappagh. Their meaning was long thought to
have been lost in time. The OPW writes that the
Boheh stone’s chief feature is the “cup and
ring” rock art, but has nothing to say about its
meaning. The Cross Man stone is unmarked,
and largely unknown, as it and kept turned face
down in a field. The farmer who owns the land
around the Lankill stone deters visitors. So
despite the rarity of their decorations, they
remain obscure. Researching the book Mayo
Atlantis, I began to suspect that the Boheh
stone could be a star map. The pattern on the
Boheh stone does not, however,r look at all
familiar to someone who knows the northern
night skies.
Yet Mayo Atlantis recounted Philip Callahan’s
discovery that the round towers of Ireland
mapped out the precession of the equinoxes.
This phenomenon is caused by earth’s tilt of 23
degrees from its axis which means the night
sky changes gradually over thousands of years.
I would have to look back in time to see what
the night sky looked like thousands of years
ago.
Folklore and legends record that some of
Mayo’s megaliths are more than 6,000 years
old, so I started my search of the night skies
over Boheh using astronomy software
Stellarium, setting the elevation for Boheh at
100 metres above sea level in the year 4,200
BCE. Not finding any obvious correspondence
with the constellations of the northern sky, I
turned the direction south, and was astonished
to see the Southern Cross standing just over
the southern horizon.
It was instantly clear that the Cross Man
stone was a rendering of the Southern Cross.
The vertical line of the cross in the Cross Man
is leaning slightly to the right, just as the
Southern Cross is leaning to the right on the
southern horizon. The tip of its hat marks the
star Gamma Centauri.
To the left of the Cross Man is an elaborate
MayOMG
Mayo’s decorated megaliths
rewrite the history of Mayo
and the world: and features
at Westival in Westport
By Rónán Lynch
box. The top corners represent Alpha Centauri
and Beta Centauri, which point to the top star
of the Southern Cross. But more astonishingly,
a line is drawn between the stars that is
bisected by a perpendicular line.
The southern celestial pole is not currently
marked by any star. Sailors instead triangulate
the position by following the vertical line in the
Southern Cross to the point where it intersects
with the line drawn from the perpendicular
between Alpha Centauri and Beta Centauri. The
Cross Man is also mathematically accurate.
Then the Boheh stone patterns also fell into
place. On the top stone, which is perched on
the rock, stands the southern cross and some
of the stars of Centaurus. There are 250 stars
carved onto this rock in precise arrangements.
All three stones display the Southern Cross.
The carvings suggest that their creators —
more than six thousand years ago — understood
the precession of the equinoxes, whose
discovery is credited by historians to
Hipparchus, the Greek scholar of the second
century BCE who is also credited with founding
trigonometry.
It now appears that the people who lived in
Ireland 6,200 years ago understood well the
precession, and marked the Southern Cross as
it disappeared from a 6,500 year cycle through
the skies over Ireland from around 10,600 BCE
to 4,100 BCE.
The Lankill stone is less directly a map of the
stars, but does have a cross within a circle of
remarkably similar proportions to the Cross
Man stone on both sides, over concentric
circles.
When seen from above, the three stones
form a triangle — or three points of a cross.
So who carved these stones? Until the
1800s it was widely believed that they are
stones created by druids. The past is not so
far behind.
Three Stones features at Westival 2023, opening
on Thursday 26 October at 6pm in the gallery
opposite Westport Plaza Hotel. More
information on irieland.co.
Cross Mn
CULTURE
